This invention relates to a device for storage of hazardous material, especially heat-producing hazardous material, such as radioactive spent nuclear fuel. More particularly, the invention relates to a device having a substantially cylindrical reinforced concrete body with an axially elongate storage space for the hazardous material.
Devices of this kind can be used both for temporary and short-term storage, such as interim storage while awaiting reprocessing or other treatment in the case of spent nuclear fuel, and for long-term storage.
WO96/21932 and DE-A1-3515971 show examples of prior art embodiments of such devices.
In the embodiments which are known from these publications, and also in other prior art devices of the same general kind, the concrete body has a central storage space for accommodating the hazardous material. The concrete wall surrounding the storage space, the thickness of which is much larger than the width of the storage space, is reinforced in three dimensions.
In the embodiment shown in WO96/21932 the reinforcement comprises axial pre-stressed reinforcement cables or rods arranged in a ring between the storage space and the cylindrical outer surface of the concrete body, and a pre-stressed reinforcement wound about the outer surface. Naturally, the latter reinforcement is applied only after the concrete body is cast and hardened at least to some extent.
The concrete body of the embodiment shown in DE-A1-3515871 also has a central storage space for accommodating the hazardous material. However, in this embodiment the reinforcement is distributed over the entire cross-section of the wall of the concrete body and completely embedded in the concrete.
The device according to the present invention is characterised in that a pre-stressed reinforcement having reinforcing members which run helically about the storage space is provided in the concrete body adjacent the outer side thereof. Preferably, the reinforcing members are arranged in two groups, one within and adjacent the other, the hand of the reinforcing members of one group being opposite to the hand of the reinforcing members of the other group. The reinforcing members may be rods, cables or wires.
With this construction of the device, the concrete body has a very effective reinforcement that is also advantageous from a production point of view.
According to a feature of one embodiment of the invention the concrete body is provided with end covers, suitably of steel, in which the reinforcing members are anchored.
The end covers offer possibilities of a simple and effective connection of the reinforcing members to pre-stressing devices and anchoring devices and also of a desired distribution of the tensioning force over the end faces of the concrete body and of introduction of the lifting forces into the concrete body through the reinforcing members.
Moreover, the end covers can be used for anchoring lifting aids, such as lifting eyes or other devices for connecting lifting hooks, lifting yokes or the like to the storage device.